1. Technical Field
The disclosure relates generally to electric field stress shielding, and more particularly, to an insulated conducting device for electrically shielding a structure at a voltage.
2. Background Art
Ion implantation is a standard technique for introducing conductivity altering impurities into, or doping, semiconductor wafers. A typical ion implantation process uses an energetic ion beam to introduce impurities (ions) into semiconductor wafers. During ion implantation, a source feed material is energized to generate an ion beam, and the generated ion beam needs to be accelerated by an acceleration column at a high voltage, for example, 670 kV. A voltage structure (usually referred to as a terminal) is used to provide the high voltage.
A co-pending U.S. patent application Ser. No 11/527,842 filed on Sep. 27, 2006 discloses an insulated conductor used as an electrical stress shield for a voltage structure in an ion implantation device, which is herein incorporated by reference. FIG. 1 shows a perspective view of a voltage structure 400 disclosed in Ser. No. 11/527,842. Referring to FIG. 1, voltage structure 400 may include a base, one or more upstanding sidewalls 404 coupled to the base, and a top 402 coupled to the one or more upstanding sidewalls 404. One upstanding sidewall 404 may have a door 440 with a handle 442 to provide personnel access to the internal cavity of voltage structure 400. Voltage structure 400 may have one upstanding sidewall 404 manufactured of one solid material piece or any plurality of separate pieces. Although illustrated as a solid piece, top 402 of voltage structure 400 may also be fabricated of a plurality of spaced conductors forming a type of conductor mesh to allow air to flow through the openings of the mesh.
One or more insulated conductors 412 may be disposed about portions of the exterior surface of voltage structure 400 that have excess electric stress. In FIG. 1, a top insulated conductor 412 is disposed proximate the entire periphery of a top edge 470 of voltage structure 400, and a bottom insulated conductor 412 is disposed proximate the entire periphery of a bottom edge 472. Although top and bottom insulated conductors 412 are positioned about an entirety of the periphery of the respective edges 470, 472, alternative embodiments may have additional or alternative exterior portions where insulated conductors 412 may be positioned. These portions may include, but not be limited to, horizontal edges, vertical edges, corners, and openings or interfaces where voltage structure 400 interfaces with external parts. Some external parts may include a motor, a generator, or a utility interface. In one example, a sphere shaped insulated conductor may be positioned about a corner of voltage structure 400. Insulated conductor 412 may include an insulator 416 with a dielectric strength greater than, for example, 75 kV/inch.
A plurality of brackets 422 may be coupled to voltage structure 400 and associated insulated conductors 412 to support insulated conductors 412 proximate an exterior portion of voltage structure 400. Brackets 422 may have a length to enable insulated conductors 412 to be positioned a desired distance from voltage structure 400. The desired distance may range from almost zero (nearly touching) to a maximum distance permitted by the surrounding air gap. In one embodiment, the desired distance is at least 1.5 inches. Bracket(s) 422 may be fabricated of either conductive or nonconductive material. Bracket 422 may also function as an electrical connection between voltage structure 400 and insulated conductor 412.
As shown in FIG. 1, insulated conductor 412 and insulator 416 are single continuous closed structures. The large size of a single piece insulator 416 may have problems in manufacturing, installing, maintenance, cost, and reliability.